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12
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84927822856
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B. W. Langley, S. M. Anlage, and M. R. Beasley (unpublished); B. W. Langley, Ph.D. thesis, Stanford University, 1991.
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15
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84927822855
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The slopes of the lines in Figs. 1 and 2, as well as their shape, are somewhat sensitive to the choice of vp(0) / c, which comes from extrapolation of the data to T=0. We are more confident about the slopes derived from the Y-Ba-Cu-O data because extends down to T / Tc= 0.1.
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16
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84927822854
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The Nb and NbCN films were sputtered by J. Murduck at TRW, Redondo Beach, from Nb targets in Ar and Ar-N-2 CH4 atmospheres, respectively. The Nb film has Tc= 9.2 K and residual resistivity ratio (RRR) of 4 with ρ ( 0 ) = 4 μ Ω cm and thickness 3650 Å. The NbCN film has a Tc= 15.8 K, RRR of 1.1, ρ ( 0 ) = 60 μ Ω cm, and thickness 5660 Å.
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20
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34250425065
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The BCS λ ( T ) is calculated using an isotropic scaled weak-coupling theory by the method of
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(1974)
Z. Phys.
, vol.266
, pp. 209
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Halbritter, J.1
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21
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84927822853
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By varying 2 Δ ( 0 ) / kBTc with this method one can examine the effects of strong coupling without resorting to more elaborate theories. Parameters for Nb are Tc= 9.0 K, lMFP= 130 Å, λL= 390 Å, and ξ0= ( 2 / π ) ξF= 380 Å, and for NbCN Tc= 18.0 K, lMFP= 100 Å, λL= 2300 Å, and ξ0= 50 Å.
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22
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84927822852
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S. I. Park, Ph.D. thesis, Stanford University, 1986;
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24
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84927822851
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D. M. Sheen et al. (unpublished); D. E. Oates et al. (unpublished).
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27
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84927822850
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Parameters chosen for YBaCu32 O7-δ are ξF= ( π / 2 ) ξ0= 15 Å, λL= 1400 Å, lMFP= 100 Å, and Tc= 90 K (see Ref. 18).
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41
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84927822848
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The fit values of λseries( 0 ) is close to the value of 1400 Å taken for the domains, but is quite different from the value calculated from the equation for λseries( T ). This is because fits to the data do not make use of the magnitude of the fitting function, only its temperature dependence.
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42
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84927822847
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In general we find a strong dependence of λ ( 0 ) on the temperature dependence used to fit the data (see Refs. 6–8, 11) as others have (see Ref. 5). This problem is common to all measurement techniques that do not uniquely determine a zero-temperature baseline.
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43
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84927822846
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If the weak links are taken to be grain boundaries [with a = 1 mum (Ref. 16) and Jc( 0 ) = 2 times 106 A/cm2] instead of the twin boundaries, the fit parameters are almost identical: 2 Δ ( 0 ) / kBTc= 4.5, Δstar( 0 ) = 8 meV. Hence the weak links can originate from several different kinds of defects.
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